1. Field of the Invention
This invention concerns, in general, retainers for securing two or more panels of highly differing coefficients of thermal expansion, and more particularly, retainers adapted to secure automotive outer body panels to an underlying support structure.
2. Description of the Prior Art
In applications where the aesthetic value of a product plays a dominant function in the marketing of such a product, it has for many years been common practice to utilize underlying structural support members with overlying aesthetically appealing outer panel members. Obvious examples of this are both small and large appliances, small office machines, snowmobiles, as well as automotive panels. In all of these applications, it is becoming increasingly advantageous to utilize light weight, flexible plastic panels installed over steel structural support body members. Utilizing plastic to obtain aesthetically appealing forms is extremely desirable over utilizing metal materials in that not only is it less costly, but the manufacturing problems associated with obtaining the ultimate aesthetic form is considerably easier. One such application is the add-on styling packages currently in use by the major automotive manufacturers, in which items such as fender flares, rear deck spoilers, and front deck lid bonnets are mounted onto existing steel structures or panels to provide a particular styling appeal to the basic lines of the automobile.
The current trend to lighter weight vehicles also renders quite attractive the potential use of light weight plastic or aluminum panels to provide aesthetically appealing outer contours of the vehicle. These panels are mounted over an underlying structure of metal which provides a structural integrity for the vehicle. Further, the increasing public pressure for automotive body panels less subject to damage under minor impact also makes the use of flexible plastic materials for outer body panels an attractive solution to this problem.
However, an ever-existing problem in early design efforts to provide compatible plastic outer panel members with underlying metallic structural members has heretofore remained unsolved. That problem arises from considerably different coefficients of thermal expansion between the materials mentioned above and the steel from which the understructure is usually constructed. That is, in a situation where direct mechanical joining of such a panel of plastic to the steel fender or inner fender, buckling or rippling of the plastic panel occurs as the members undergo a wide variation in temperature. This buckling or rippling becomes totally objectionable at junctures of the plastic panel and the steel member where visible blends occur; such as in the add-on fender flares and the rear deck spoiler mentioned above.
This situation precludes the use of visible mechanical fasteners at the juncture, and the usual approach has involved use of fasteners hidden within the inner panel cooperating with retainer strips or studs which engage an inner lip of the outer panel. Since the fasteners are in a matrix of steel, the spacing of the pressure points applied to the plastic panel thermally "grow" more slowly than the retainer panel, hence the objectionable ripple effect which is aggravated by the remote location of the fasteners from the seam or blend line.
It is an object of the present invention to provide a retainer arrangement in which panel members of materials having greatly dissimilar rates of thermal expansion may be joined without the appearance of unsightly rippling or bulging of the outer panel as the assemblage undergoes substantial temperature variations.
It is a further object of the present invention to provide a retainer arrangement which accommodates physical blends or joints between the respective panels without the need for exposed mechanical fasteners.
It is still a further object of the present invention to provide a retainer arrangement suitable for automotive body panel applications in which an outer panel is joined to an underlying support structure having greatly dissimilar coefficients of thermal expansions.
It is yet another object of the present invention to provide a retainer arrangement suitable for automotive body applications that does not detract from the aesthetic appeal of the vehicle.
It is still a further object of the present invention to provide a retainer arrangement for automotive panels with highly dissimilar coefficients of thermal expansion that is economical to manufacture and aesthetically acceptable.
Yet another object of the present invention is to provide a retainer arrangement for automotive panels of dissimilar coefficients of thermal expansion which makes possible the use of automotive outer body panels less subject to damage under minor impact, as well as contribute to lightening the weight of the over all vehicle.
Further objects and advantages of the invention and the nature of the invention will be clear to those skilled in the art from the succeeding detailed description of the preferred embodiment of the invention and the accompanying drawings thereof.